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Spontaneous ruptures of the distal biceps tendon may be a marker of wild-type transthyretin (TTR) cardiac amyloidosis, a single-center study found, potentially giving physicians an easy way to determine the underlying cause of heart failure with preserved ejection fraction (HFpEF) in some patients.

When the tendon is ruptured, patients develop a bunching of the biceps upon flexion of the arm against gentle resistance. This condition in one or both arms was observed in , compared with 1 out of 40 controls (a patient who did not have amyloidosis ruled out by technetium pyrophosphate imaging, at that).

"Based on the histologic studies of tendons and ligaments in older patients, rupture of the distal biceps tendon may represent TTR amyloid deposition in the biceps tendon, similar to carpal tunnel syndrome," wrote Rodney Falk, MD, of Brigham and Women's Hospital in Boston, and colleagues in the September 12 issue in the Journal of the American Medical Association.

"Early diagnosis of wild-type TTR cardiac amyloidosis is important because trials are under way investigating therapies to halt disease progression. The finding of [this tendon rupture], an easily elicited diagnostic sign, in a patient with HFpEF should raise suspicion for wild-type TTR cardiac amyloidosis."

Pfizer now has a TTR amyloid cardiomyopathy drug, tafamidis, in a .

"This observation underscores the continued importance of physical examination in an era of extensive diagnostic testing," the investigators added.

"The clinical importance [of this study] is that the detection of a ruptured distal biceps tendon may be a clue for the diagnosis of wild-type TTR amyloidosis as the cause for heart failure. This diagnosis is often overlooked in clinical practice, so this relatively simple evaluation could increase detection of the disease," said Stuart Katz, MD, of NYU Langone Health, in an email to MedPage Today. "Enhanced detection could lead to better treatment."

"This is an interesting finding that warrants further prospective study in a multisite cohort," continued Katz, who was not part of Falk's group. "The observed rate of tendon rupture in the control group was 1/40, whereas the expected rate is 1/1000. This could occur by chance, but it is also possible that occult amyloidosis was present in the control group."

The TTR cardiac amyloidosis arm of the present analysis consisted of consecutive patients presenting to the Cardiac Amyloidosis Program at Falk's institution. Patients with common non-amyloid etiologies of heart failure were recruited as controls.

Tendon ruptures occurred largely in the dominant arm of each patient, with one-quarter of patients with them developing ruptures in both arms.

Of those who had a rupture, 37.8% didn't know it. Those who were aware reported that the distal biceps tendon ruptured approximately 5 years prior to heart failure diagnosis.

"Precise estimates of the prevalence of wild-type TTR amyloidosis as a cause of heart failure are lacking and would affect the positive predictive value," Falk and colleagues acknowledged.

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